Ecological and evolutionary opportunities of apomixis: insights from Taraxacum and Chondrilla

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Abstract
The ecological and evolutionary opportunities of apomixis in the short and the long term are considered, based on two closely related apomictic genera: Taraxacum (dandelion) and Chondrilla (skeleton weed). In both genera apomicts have a wider geographical distribution than sexuals, illustrating the short–term ecological success of apomixis. Allozymes and DNA markers indicate that apomictic populations are highly polyclonal. In Taraxacum, clonal diversity can be generated by rare hybridization between sexuals and apomicts, the latter acting as pollen donors. Less extensive clonal diversity is generated by mutations within clonal lineages. Clonal diversity may be maintained by frequency–dependent selection, caused by biological interactions (e.g. competitors and pathogens). Some clones are geographically widespread and probably represent phenotypically plastic ‘general–purpose genotypes’.